Sculptris Pro Reduces My Undo History

Sculptris Pro works very differently from traditional subdivision sculpting.

With standard subdivision workflows, brush strokes simply move existing vertices. In contrast, Sculptris Pro dynamically adds and removes polygons with every stroke, constantly recalculating topology as you sculpt.

Because each stroke can significantly change the mesh structure, the Undo system must store much more data than it would with traditional sculpting. This makes Sculptris Pro inherently more memory-intensive.

On systems with ample RAM, this typically goes unnoticed. However, on systems with limited available memory, ZBrush may need to manage resources dynamically. When memory becomes constrained, ZBrush may reduce or clear portions of the Undo History in order to allow sculpting to continue smoothly.

In extreme cases, this can result in very limited or no Undo History being available.

Reserved Undo Memory Setting

ZBrush includes a setting at:

Preferences > Undo History > Reserved Undo Memory

This value determines how much memory ZBrush reserves specifically for storing Undo data.

Setting this value to 0 removes the limit and allows ZBrush to use as much memory as possible for Undo History.

Important

This is generally not recommended.

When Reserved Undo Memory is set to 0, ZBrush may begin writing large amounts of temporary data to disk once system memory is exhausted. This results in frequent “Compacting Memory” operations, which can significantly slow down performance and interrupt your workflow.

For most users, it is best to leave the Reserved Undo Memory setting at its default value and allow ZBrush to manage memory automatically.